I defined this equation and graph a while ago, but it certainly hit home tonight. I made what I consider to be probably the largest and most embarrassing design error I have ever made. While the repercussions of the error were not all that significant, the simplicity of it makes it sting even more so. I managed to talk myself into making a very, VERY basic engineering mistake. In short, bending loads are a bitch.

I over thought myself. And when this happens, the following will always be true:

The equation utilizes the rule of pi (the fact that for any project the amount of time, effort and money required will always be 3.14159 times your initial expectations, while payoff will 3.14159 time less, with the chance of failure being 3.14159/amount of sleep in the past 24 hours) and a few constants and functions relating mostly to attempts to be clever.

Note that as time thinking increases, you reach an inversion point where the likelihood of failure increases and, initially, begins to oscillate randomly. This corresponds to that point in any project when we begin to rethink our design and try to be “clever.” Note that the chances of failure momentarily reach a negative failure. This is the epiphany moment. Every project has one, though it is brief and 99% of the time we will pass through this moment and never realize it until it’s too late.

So what did I do wrong in my case? I tried to be clever. I had a simple design, and decided that I could improve it. I realized that the loads were not ideal, but spent so much time thinking about it that I convinced myself it wouldn’t be an issue. Oh was I wrong. I knew deep down that there was a chance that it could all end poorly. Maybe that’s why I left a plan B to return all items to the original state.

I could come up with a long list of reasons why this isn’t all my fault, and things that should have been done differently. Some could have some merit. But in the end, I suggested the solution, built the product and realized the bending load, and allowed it to remain. And it cost a group of people a significant amount of valuable time on a very important project. While I certainly have egg on my face after this, it has reminded me of the importance of the engineering process and the fact that we can all make mistakes (and not to be so critical when other make those mistakes.) So long as we use these moments to learn and grow not all is lost.

And in conclusion, I leave you with the wise words of Pat Clarke: “The trick is, There is no trick!”

I recently was asked to teach a suspension seminar as a guest lecturer for the WPI Motorsports club. If you would like a copy of the slides from my lecture you can view them here:

http://www.tuneddesign.com/Seminars/Sus_101.ppt

I still find that I struggle to succinctly describe suspension design and theory. It is such a broad topic, and requires a in depth discussion of the physics of vehicle dynamics which tends to either bore or confuse/scare most. I’ve been working with vehicle dynamics for 5-6 years now and still find myself reaching for reference material on a regular basis.

With my current round of Engine tuning articles wrapped up (though I am far from done with this topic!) I am going to focus on the same approach for suspension. I still believe I can use the same approach and break it down into the basics with out requiring a PhD. in advanced mathematics to understand. Maybe I can keep fooling you guys into believing I know more than I do. At least I can still stall and sound like I know what I am talking about until I figure it out.

Much like that annoying neighbor or mooching family member, your engine is something you would rather not come knocking. Knock is a warning and indication of potential and pending trouble. Thankfully there are some simple tools to monitor and determine knock and help tune your engine to prevent the conditions which lead to knock and pre-ignition.

The physics

Knock and pre-ignition are phenomena that describe improper or uncontrollable combustion, and both lead to reduced performance and drivability and can even cause catastrophic engine damage. Understanding what these terms describe, the physics behind the phenomenon, why they occur and how to prevent them is the most critical aspect of tuning your engine, as a mistake here will essentially guarantee eventual engine failure.

Ignition

To fully understand the phenomena we must first discuss and understand the basic ignition process itself. Recall that an engine is essentially an air pump and relies on changes on pressure to move air in and out of the engine. Ignition of the air/fuel mixture is initiated by the spark plug when either the ECU or distributor signals the ignition coil to fire. This causes expansion of the previously compressed gas mixture.

Proper timing to ensure maximum power requires ignition of the mixture at the peak pressure in the cylinder. However, since ignition is not an instantaneous event and the flame front propagates through the combustion chamber. This requires the initial spark event to occur Before Top Dead Center (BTDC) and is always measured in degrees of rotation in reference to top dead center. When tuning ignition timing in an ECU map it is these values that are being modified. Typically positive values indicate degrees BTDC while negative values are ATDC.

Timing the spark event to ensure full ignition of the mixture always occurs at peak cylinder pressure will create the most torque from the engine being tuned. The key is to have as little timing advance as possible, while still maintaining this pressure – this is a torque limited ignition mapping method and the value may be referred to as the Mean Best Torque Spark Advance and should always be the target when not limited by engine behavior such as knock or pre-ignition. This is precisely why monitoring and controlling knock is so important.

Knock

Knock, pinging and detonation describe improper propagation of the flame front – in other words, the air/fuel mixture is burning in an inconsistent and unpredictable rate. This causes the final ignition event to occur at a time other than peak cylinder pressure and a decrease in pressure. This can be caused by many issues, including incorrect spark timing, failure of the fuel to atomize, or local hotspots in the combustion chamber. This will cause multiple areas of ignition not in the same location as the flame front. This can be basically described as the ignition force “jumping” around the combustion chamber, rather than coming from one location.
The result is each of these ignition events producing its own pressure or shockwave. These waves propagate from the local ignition point, and run into each other within the cylinder. The result is a combined shockwave resonating at a different frequency than normal combustion and even creates an audible metallic knock or pinging noise, hence the name of this phenomenon. This can case holes in engine components and small indents on the piston face as well as very rapid wear and stress on all engine components.

If knock occurs at an ignition timing value less advanced then that for best torque, the engine is said to be knock limited, as ignition timing is tuned to prevent knock at this map location rather than for maximum torque. This is often the case in higher compression and force induction engines, where pressure and temperature in the cylinder can be very high. The key is to request as much spark advance as possible while avoiding knock during any engine operations and parameters.

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Ah, Thanksgiving and the beginning of the holiday season and all that comes with it. Changing of the leaves, the smell of pies cooling, eating ourselves into a turkey coma, and enjoying kicking back with a cold drink and watching our favorite violent sport – Black Friday Holiday shopping. If only everyone would learn to be anti-social like me and do all their shopping online…  Seems as though the american past tradition of camping now is only practiced by crazed shoppers in parking lots and what appears to be a group of liberal arts students having a crafts fair with tents and hand painted signs (I think I am supposed to call them protesters?)

I work hard for my vacation time, and can’t help but think that there’s a few things I’d be doing with my time off than camping for a week to pick up cheap video games or TVs. My Nintendo with the original Zelda and 32″ LCD HD TV are still doing just fine for me thank you very much. Then again, I am not really the camping type. As Ron White said, I wouldn’t go camping for a week if I were camping.

This time of the year also brings a tradition for us gear heads – this is the weekend all the toys go away for the winter. In these temperatures the ride on my summer tires leaves a feeling comparable to an initiation ceremony for the Omega Theta Pi fraternity. The tires on the Ducati don’t fair much better, and as hypothermia sets in I am thankful for the usually uncomfortable “up the leg” routing of the exhaust and the under seat outlet setup at least keep my nether regions free of frost bite. These and the other toys are thus sent to the garage to join the formula car for their winter hibernation. All filled up on fuel stabilizer, straight water replaced with an anti-freeze coolant mixture, and their shoes removed, wrapped and kept off the cold floor and tucked into under the covers with love and care.

This is generally a sad event marking the beginning of that long count down till the snow, salt and sand are gone and we can welcome the season with a healthy dose of tire smoke. However, all this down time does tend to create another kind of craze in our kind  sometime akin to the illogical and slightly obsessive behavior of those black Friday shoppers: we take our toys apart, and try to make them faster, turn harder, or look better. I have a few things planned for this Modding Season, but those are still top secret for the time being.

So, what do YOU have planned for this winter? Engine swaps? Tuning? New Paint? Ground Up build? Share!

Time to start posting regularly again now that my smart phone dilemma is in order and the “regular job” has calmed down again.

The FT-86: If you haven’t heard of this yet you have been living  under a rock (or hiding from tuner fan boys)

The resurrection of the drifting cult hero car – the new hachi has certainly generated excitement and possibly a few wet dreams in the import tuner crowd. With its Subaru based 200hp in a ~2600 lb chassis, rwd, LSD on manual cars and a wide array of the toys that make us giggle like school boys finding our dad’s “ahem “special magazine collection” – it’s no surpise,

Can this car deliver on the hype though? So far Toyota has been mum on official specs and details. The specs that have been circulating the internet as the official numbers come from a leaked training manual in Japanese. If the car delivers, and at the price being rumored of around $20k, it will be quite the contender. I can’t help think that there might be some disappointed young men re-watching their Initial D collection to cope when this car hits the showroom. Anyone remember the Hyundai Genesis? Hype.

I will be writing a little more on this soon and will be watching the developments as this car makes it’s way to the showroom. For now what are your thoughts? Will the car be all it’s hyped up to be? Discuss.

Launch Control
What is it, how does it work and do I need it?

A proper launch is key to success in any level racing. Eliminating wheel spin and wheel hop, maximizing traction, weight transfer and power off the line, and in forced induction car, to build boost before launch are all critical components in the launch of any vehicle. The ability to do all of these consistently and in a controlled fashion with as little impact to the vehicle as practical is key to success in any level of racing. Sophisticated traction control systems can aid in the traction and wheel spin areas, but work by limiting your power. This can seem counterintuitive when you “want to go fast.” In addition, true traction control systems sophisticated enough for racing applications are available only in a handful of exotic cars with a price tag much out of the traditional “tuners” budget. The solution for all of these problems, however, is quite simple: Launch Control.
What is launch control, and how does it work?

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And tend to make predictions that are usually shortly proven to be very false. Anyone recall when it was claimed to be physically impossible to break 300 MPH?

It seems to be happening again (and has for a while). And may lead to a rules change that some FSAE teams need to keep in mind.

http://fsae.com/eve/forums/a/tpc/f/125607348/m/14820986051

I can attest to the amazing cornering power these cars having had seat time in quite a few. With the push to make these cars lighter and lighter the cars have become significantly smaller. Many cars still target the same wheelbase/trackwidth only exacerbating the danger. It is quite surprising the 1.7g requirement has never been revised especially considering the aggressive focus on safety and the changes in the rules reflecting as much.

Something to consider for all the FSAE teams, weather required by the rules or not. I know one particular FSAE team that narrowly passed the static rollover tilt test last year that will receive a personal note on this matter.

Formula SAE registration took place for Michigan and Lincoln NE (the new location for FSAE East) today – looks like the slots filled up quickly again this year. I am glad to see a waitlist finally implemented.

WPI is in and car number 83 for the Michigan event. Tuned Design and Tuner Tools will be attending this year. Good luck to all the teams and see you in May! (And of course get in touch if you need any part or help)

Tweaking the Recipe
Understanding, Determining and Tuning target Air/Fuel Ratios utilizing oxygen sensors and wideband controllers
If you’ve been following the past posts (Volumetric Efficiency Explained and Load Calculation and Control) you should have a grasp on the basic recipe for tuning your engine. Similar to that secret family recipe variation of a common dish though, this mix requires personalized tweaking to take it from just a basic out of the box “heat-and-serve” style tune to something unique and optimized for your vehicle. This process requires patience, attention to detail and just a dash of artistic flare. The good news, however, is that there are many tools that are easily accessible the helping you with this task, and some of them may even already be installed on your vehicle from the factory.

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